In the course of manufacturing a semiconductor device, various liquid processes, such as a wet etching process, a chemical liquid cleaning process, etc., are performed on a substrate such as a semiconductor wafer. A single-wafer processing unit for performing these liquid processes includes a spin chuck that rotates the substrate around a vertical axis line while holding the substrate horizontally; a nozzle through which a processing liquid is supplied onto the substrate being rotated; and a cup that receives and collects the processing liquid dispersed from the substrate after supplied thereto.
The cup has a top opening at a central upper end thereof and an exhaust port at a bottom portion thereof. The top opening of the cup has a diameter slightly larger than that of the substrate. If the inside of the cup is suctioned through the exhaust port, a gas (typically, clean air) that exists in a space above the substrate is drawn into the inside of the cup through the top opening and exhausted through the exhaust port. The cup is provided with a wall for guiding a flow of the gas within the cup (see, for example, Patent Document 1). By allowing the gas to flow within the cup at an appropriate flow rate in a proper direction, the processing liquid once dispersed from the substrate can be suppressed from re-adhering to the substrate, and mist of the processing liquid can be removed from the gas.
It has been required to perform the exhaust effectively even with a low suction force from the exhaust port. In this regard, there still is a room for improvement in the wall structure described in Patent Document 1.
Patent Document 1: Japanese Patent Laid-open Publication No. 2014-086639